1. Field of the Invention
This invention relates to fusion processes for production of granular metal soaps by reaction of metal oxides and higher monocarboxylic acids in the presence of a catalyst.
2. Prior Art
Granular metal soaps such as zinc soaps are used as waterproofing agents, lubricating or anticaking agents and thickening or suspension agents. The soaps also are useful as stabilizing agents for plastics.
The production of granular metal soaps by various processes, including precipitation and fusion processes, is known in the art. Precipitation processes generally produce metallic soap by reaction of an aqueous solution of a water-soluble metal salt and a fatty acid alkali metal salt, whereupon the metal soap precipitates out of solution. These precipitation processes require time consuming filtering, washing and drying steps to isolate a purified product from the aqueous reaction mixture. Fusion processes, however, produce metal soaps by the reaction of metal oxide, hydroxide, carbonate or acetate with a molten fatty acid at temperatures sufficiently high to form the metal soaps, and often avoid the separate filtering, washing and drying steps. Most commercial fusion processes produce large lumps of metal soap which must be ground to a desired size.
U.S. Pat. No. 3,803,188 discloses a process for producing metal soaps by dispersing finely ground metal oxide in molten fatty acid (well below the melting point of the desired soap), adding water and allowing the reaction to proceed (about 10 to 30 minutes) below about 110.degree. C. while stirring. The reaction product is milled to a desired size.
U.S. Pat. No. 4,307,027 discloses a continuous process for the preparation of dry metallic soaps of higher fatty acids in a plug flow reactor. Metal oxides or hydroxides and fatty acids are combined, optionally in the presence of a catalyst such as water, a nonionic emulsifier or a caustic solution, and heated to a reaction-inducing temperature in a stirred tank reactor for 10 to 80 minutes. The heated reactants are continuously fed to a plug flow reactor where they reside for about 2 to 60 minutes. Solid reaction products are continuously discharged from the plug flow reactor and fed to a hammer mill to obtain a coarse ground product. The coarse ground product is fed to a jet mill for further size reduction so that less than 0.1% is retained on 325 mesh.
U.S. Pat. No. 4,294,771 describes a "method for producing metal soaps in dust-free granulate form without any grinding step." Fatty acid, metal oxide, hydroxide or carbonate, and 1 to 5% water (based on the weight of the fatty acid) are heated and agitated in a closed vessel. Temperature and pressure increase as the exothermic reaction proceeds over the course of 10 to 15 minutes. After completion, the added water as well as the reaction water are drawn off under decreased pressure during agitation. A granular soap remains.
Fusion processes generally employ catalysts to produce a more rapid reaction at a lower temperature. Japanese Patent No. 59/170035 discloses the reaction of fatty acids with zinc oxide or calcium oxide in the presence of a polycarboxylic acid such as phthalic acid, citric acid, or succinic acid at 130.degree. C. for 35 minutes.
Prior art fusion processes generally have one or more deficiencies, such as requiring separate grinding steps, using inefficient batch processing techniques, requiring relatively expensive and/or large equipment, having long inefficient reaction times, etc.
It is an object of the present invention to utilize a dry fusion process to rapidly produce a granular metal soap.